The invention relates generally to safety valves, and in particular, to a safety valve that is automatically closable upon an inadvertent drop of pressure in a fluid downstream from the safety valve.
Flowlines utilized by the oil and gas industry have many devices such as gauges associated therewith. These devices are relatively fragile so that on occasion they are broken during the normal operation of the flowline. This, of course, results in a fluid product being exposed to the atmosphere which can in many instances be highly undesirable inasmuch as many flowlines carry products which are harmful to the environment as well as to the health of persons coming in contact therewith.
Heretofore, valves which are automatically closable upon an inadvertent drop in pressure in a fluid flowline have generally been of a somewhat complicated structure utilizing springs, pressure operated diaphragms and the like, and are exemplified by U.S. Pat. No. 3,618,689 issued to German, U.S. Pat. No. 3,628,562 issued to Bruins, and U.S. Pat. No. 3,661,173 issued to Bauer. U.S. Pat. No. 3,949,786 issued to Houston shows a safety valve which utilizes a ball contained loosely within a chamber and arranged so as to engage a valve seat when there is a sudden pressure drop in the flowline thus preventing flow. While these patents show devices which appear to be closable upon a drop in flowline pressure, some of them show a relatively complicated structure and all of them appear to create fluid-tight seals at only one location.
In the light of the serious consequences which could result if such a safety valve malfunctioned at its sole sealing location, it would be highly desirable to provide a safety valve that creates fluid-tight seals at a plurality of locations.
Oftentimes a gauge or the like that receives pressure from the safety valve needs to be changed or repairs made to so that pressure to the gauge must be shut off when desired. Thus, it would be highly desirable to provide a safety valve that can be selectively shut off.